1. Field of the Invention
The present invention relates to a headlamp for a vehicle and, more particularly, to a headlamp providing an enhanced visibility.
2. Related Art
In some headlamps for a vehicle, for example, a lamp unit having a light source is disposed in an outer housing of a lighting device constituted by a cover and a lamp housing.
For example, there is a projector type lamp unit for a vehicle having a projection lens for forward projecting a light emitted from a light source, a reflector for reflecting the light emitted from the light source toward the projection lens side, and a shade for shielding a part of the light reflected by the reflector.
In some projector type lamp units, for example, a rotary shade, which is rotatable around its rotary axis extending in a vehicle width direction, is employed (see Japanese Patent Unexamined Publication JP-A-2006-202694).
In a headlamp for a vehicle described in the JP-A-2006-202694, the rotary shade is rotated between a shielding position and a shield resting position. A low beam light distribution pattern, which lights a position at a short distance, is formed when light is emitted from the light source while the rotary shade is placed in the shielding position, and a light distribution pattern for a high beam, which lights a position at a long distance, is formed when the light is emitted from the light source while the rotary shade being placed in the shield resting position.
The light distribution pattern for the low beam is formed by two patterns including a pattern for mainly lighting a road surface and an overhead irradiating pattern for mainly lighting a road sign thereabove.
The light distribution pattern for a high beam is formed by a single pattern, and the light is mainly irradiated on the road surface by a light turned downward in a horizontal direction and the light is mainly irradiated on the road sign by a light turned upward in the horizontal direction.
In the conventional headlamp for a vehicle of the JP-A-2006-202694, however, the overhead irradiating pattern is not changed depending on a running state, for example, a state where a vehicle runs over an ordinary road or a state where the vehicle runs over a highway. In some cases, therefore, visibility for a road sign is poor depending on the running state.
Moreover, because the overhead irradiating pattern is not formed depending on the running state, there is a fear that a light forming the overhead irradiating pattern might be a dazzling light for other vehicles, such as cars running ahead.